chore(deps): bump kotlinVersion from 1.3.30 to 1.3.31 (#258)

Bumps `kotlinVersion` from 1.3.30 to 1.3.31.

Updates `kotlin-gradle-plugin` from 1.3.30 to 1.3.31
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.3.30...v1.3.31)

Updates `kotlin-stdlib` from 1.3.30 to 1.3.31
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.3.30...v1.3.31)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

build.gradle

@@ -1,7 +1,7 @@
 buildscript {
     ext {
         javaVersion = '1.8'
-        kotlinVersion = '1.3.30'
+        kotlinVersion = '1.3.31'
 
         // see https://www.jetbrains.com/intellij-repository/releases/
         intellijVersion = '191.6183.87'